Scavenger plate for pump inlet

ABSTRACT

A plate structure disposed between the end of a pump rotor and an inlet port provided in an associated pump housing, the plate being effective to withdraw liquid from around the outside of the rotor when the rotor is rotated, and direct the liquid radially inwardly towards the axial center of the pump and rotor, and into the flow stream entering the rotor.

provided in an associated pump ective to withdraw liquid from 1' whenthe rotor is rotated, and rdly towards the axial center of FOREIGNPATENTS 3/1967 White.....

2 1950 10/1919 Switzerland..................

Paul H. Scheffler; Jack L. McCabria, both of Lima, Ohio 813,411 Apr. 4,1969 [45] Patented Oct. 19, 1971 Westinghouse Electric CorporationPittsburgh, Pa.

4 Claims, 2 Drawing Figs.

References Cited UNITED STATES PATENTS 6/1948 Unlted States Patent [72]Inventors [21] AppLNo.

[22] Filed [73] Assignee [54] SCAVENGER PLATE FOR PUMP INLET 51] [50]FieldofSearch........,...................................

PATENTEUBU 19 |97| INVENTORS Paul H. Scheffler 0nd r3 ATTORNEY Jock L.McCobrl 2 V 2 m C! WITNESSES SCAVENGER PLATE FOR PUMP INLET BACKGROUNDOF THE INVENTION The present invention relates generally to pumps, andparticularly to pumps for pumping molten metals.

In copending applications Ser. No. 610,935 filed Jan. 23, 1967 by P. H.Scheffler, and now U.S.'Pat No. 3,459,133, Ser. No. 761,024 filed Sept.20, 1968 by P. H. Scheffler et al.-, both assigned to the presentassignee, there are disclosed pump structures capable of pumping liquidor molten metals in an effective and efficient manner. The disclosedstructures include generally an elongated rotor vertically disposed inan associated inlet housing. the lower end of the rotor being locatedabove an inlet port provided in the lower end of the housing. The rotorhas an inlet port (or ports) located above the housing inlet port, andinternal passageways and vanes extending the length of the rotor, thevanes and passageways providing the pumping action by producing a forcedvortex of liquid within the rotor when the rotor is rotated.

Between the inner diameter of the housing and the outer diameter of therotor is a relatively narrow annular space which fills with the liquidor molten metal when the lower end of the pump is disposed in the vat orcontainer which contains the liquid to be pumped. Liquid from thedischarge end of the rotor drains into this annular space during certainmodes of operation of the pump since a positive seal is not provided atthe rotor discharge. The liquid within the annular space must be removedand continuously scavenged when the rotor is rotating to prevent aself-perpetuating disturbance from acting upon the rotor. Thisdisturbance is produced by an uneven displacement of the liquid withinthe annular space. If the rotor is displaced a radial distance from thecenter of the housing, because of vibration or by misalignment oreccentricity in the assembly, a converging passage and a divergingpassage are produced in the space around the rotor. The circumferentialflow of liquid in the converging passage generates a positive pressureand force in an inward direction towards the center of the rotor, andthe flow in the diverging passage generates a negative pressure andforce which acts outwardly and away from the center of the rotor. Theresultant of these two forces acts through the center of the rotatingrotor in a direction perpendicular to the radial displacement of therotor within the annular space. Thus, the rotor moves in acircumferential direction to a new location where the hydraulic forceswill again be directed perpendicular to the new displacement.

The resulting motion of the rotor is therefore self-perpetuating and canbe described as a whipping motion about the center of the housing. Themechanism which produces the phenomenon is the same mechanism whichproduces oil whip or shaft whip in a vertical guide bearing.

The initial displacement of the rotor may be caused by vibration, or bymisalignment or eccentricity between the rotor and housing. Accordingly,this initial displacement cannot readily be eliminated. The magnitude ofthe self-perpetuated whipping motion of the rotor can be such that therotor will contact and rub against the housing thereby increasing thepossibility of damage to both the rotor and the housing. In any case,the magnitude of the deflection is such that the pumping capacity of thepump is appreciably reduced, and the friction generated in the liquid bythe whipping rotor increases substantially the power required to drivethe rotor.

BRIEF SUMMARY OF THE INVENTION To eliminate the hydraulic forcesgenerated in the liquid metal around the rotor, and thereby maintainrotor alignment and minimum frictional losses within the housing withrotation of the rotor, the present invention includes a stationaryscavenger plate disposed between the bottom of the rotor and the bottomwall of the inlet housing. The liquid in the housing can be effectivelyscavenged" or drawn out from around the rotor by utilizing therotational velocity imparted to the liquid by the rotor, and by theejector action of the inlet ports. The bottom surface of the plate isprovided with curved bosses or vanes which deflect and direct therotating liquid radially inwardly towards the eye or axial center of thepump and thus towards the inlet port of the rotor. The ejector action ofthe port entrains the inwardly directed liquid flow into the rotorthrough an inlet orifice provided in the plate.

THE DRAWING The invention, along with its objectives and advantages,will better understood upon consideration of the following detaileddescription in connection with the accompanying drawing, in which:

FIG. 1 is a vertical section of the lower portion of a pump providedwith a scavenger plate in accordance with principles of the invention;and

FIG. 2 is a bottom plan view of the plate shown in FIG. ll.

PREFERRED EMBODIMENT Specifically, FIG. I shows, in vertical section,the lower portion of the pump disclosed in the above-mentionedapplication Ser. No. 761,024, as well as the scavenger plate brieflydescribed above and more particularly described hereinafter.

The portion of the pump shown in FIG. I is generally designated by thenumeral 10. The structure of the pump includes an elongated rotor 12centrally disposed in an elongated inlet housing 14 for rotationtherein. Between the rotor and housing is formed a relatively narrowannular space I3. The housing and rotor are provided with inlet ports 16and 18, respectively, formed by replaceable orifice structures 20 and 22suitably secured in the lower ends thereof, though the present inventionis not limited thereto. The interior of the rotor is provided withliquid directing passageways or channels 24, the channels beingconnected in fluid communication with the inlet port 18 by openings 25provided in an inlet bush ing 26.

As explained in the aforementioned] applications, the pump componentparts as thus far described are preferably cast or compacted from a heatand corrosion resistant material such as silicon carbide.

As explained earlier, the portion of the pump 10 shown in FIG. I may bedisposed directly in a bath of molten metal (not shown) to perform itspumping function, i.e., to transfer the molten metalfrom a vat or othercontainer (not shown) to another location, to circulate the molten metalwithin the container, or to circulate it between two or more containersor locations. When the housing 14 is lowered or otherwise disposed inthe bath of molten metal, the metal enters the housing through the inletport 16 to fill the space l3 between the rotor and housing. When it isdesired to start the pumping operation, the rotor is rotated causing aflow of the metal into the inlet ports 16 and 18, and through the: rotorchannels 24 as indicated by appropriate arrows. The liquid metal isdischarged from the pump through a discharge port in the upper portionthereof.

If the rotor 12 is in substantially perfect alignment with the housingI4, and if the surfaces of the housing and rotor forming the annularspace 13 are formed or finished in substantially perfect roundness, thehydraulic forces within the space 13 would be essentially balanced andthe rotor deflection problem, explained above, would be essentiallynonexistent. However, losses due to the friction between the rotor andliquid would remain a problem.

As mentioned above, the component parts of the pump are preferably castor compacted parts made from hard, ceramic materials which are noteasily and economically machined or otherwise finished to a degreeproviding perfectly round or smooth surfaced components. With suchmaterials and methods of making the pump parts, and particularly thehousing and rotor, the probability of some vibration, eccentricity, andmisalignment is always present, so that a more simple and economicalmeans is required to effect and insure the balance of the hydraulicforces acting upon the rotor 12.

In accordance with the present invention, a stationary plate structure28 is located in the space between the bottom end of the rotor 12 andthe end wall 29 of the housing 14 or, more specifically, in a horizontalplane. between the inlet bushing 26 and the orifice member 20.

The bottom surface of the plate 28 is provided with circumferentiallyspaced apart bosses or raised vane portions 30 which rest on the insidesurface of the end wall 29, the vanes being effective to space the mainbody portion of the plate from said wall and the orifice member 20. inFIG. 2, three vanesare shown, for purposes of illustration only, and thevanes are preferably curved in a radial direction, as shown, forpurposes presently to be explained.

The plate 28 is further provided with an inlet orifice 31 located inaxial alignment with the ports 16 and 18 of the rotor and housing,respectively. The plate, like the other pump components, is preferablymade of a hard, heat resistant material such as silicon carbide.

In operation, upon rotation of the rotor 12, a rotational velocitycomponent is imparted to the liquid in the annular space 13, and, as thepumping action of the rotor draws liquid through the inlet port 16, anejector action is produced at the port. The direction of the rotationalvelocity of the liquid is tangential along the fixed, inside surface ofthe housing 14 so that, without the plate 28, the tendency of therotating liquid is to remain away from the eye or axial center of thepump and the flow of liquid entering through the port 16. The plate 28,with its vanes 30, however, collects the liquid rotating in the space 13and redirects it radially inwardly towards the eye of the pump and intothe flow of liquid entering through the port 16 to be entrained thereby.The radial curvature of the vanes 30 improves their effectiveness in thedirecting the flow in a radially inward direction.

In this manner any liquid in the space 13 is moved or scavenged so thatfriction losses in said liquid, and the possibilityof unevenly displacedliquid existing around the rotor is essentially eliminated, along withthe unbalanced hydraulic forces resulting therefrom. In this manner andfor this reason,

the rotor is not deflected and the pump structure 10 of the presentinvention performs effeciently and essentially without vibration withcast components having uneven and unfinished surfaces. And this isaccomplished with a simple, economical structure, namely,'the plate 28,the plate providing further savings by permitting the use of pumpcomponents having the unfinished surfaces.

Though the invention has been described with a certain degree ofparticularity, changes may be made therein without departing from thespirit and scope thereof.

We claim:

1. In a pump structure for pumping liquids, said structure including anelongated annular walled rotor having internally axially extending vanesand an elongated walled housing disposed concentrically about saidrotor, the rotor being rotatable in the housing about a vertical axiswith an annular clearance between the rotor and the housing permittinglimited reverse flow 'therebetween, the housing and the rotor havingaxially aligned restricted inlet ports in their lower ends to admitliquid into the rotor to be pumped axially thereof, and a stationaryplate disposed horizontally in the housing between the housing and thelower end of the rotor, said plate having a restricted inlet 'orifice inaxial alignment with said rotor inlet port, and said plate having meansto direct liquid from said annular clearance through the inlet orificeto the rotor inlet port on the creation of a suction vortex by therotation of said rotor.

2. The pump structure of claim 1 in which said plate is spaced from thelower end of the housing and said means provides for liquid flow underthe plate from the annular clearance to the inlet orifice.

3. The pump structure of claim 1 in which said plate has vanes on itslower surface for supporting the plate in spaced relation to the lowerend of the housing, said vanes directing liquid from the annularclearance to flow under the plate to the inlet orifice.

4. The pump structure of claim 3 in which the vanes are curved radiallyof the plate.

1. In a pump structure for pumping liquids, said structure including anelongated annular walled rotor having internally axially extending vanesand an elongated walled housing disposed concentrically about saidrotor, the rotor being rotatable in the housing about a vertical axiswith an annular clearance between the rotor and the housing permittinglimited reverse flow therebetween, the housing and the rotor havingaxially aligned restricted inlet ports in their lower ends to admitliquid into the rotor to be pumped axially thereof, and a stationaryplate disposed horizontally in the housing between the housing and thelower end of the rotor, said plate having a restricted inlet orifice inaxial alignment with said rotor inlet port, and said plate having meansto direct liquid from said annular clearance through the inlet orificeto the rotor inlet port on the creation of a suction vortex by therotation of said rotor.
 2. The pump structure of claim 1 in which saidplate is spaced from the lower end of the housing and said meansprovides for liquid flow under the plate from the annular clearance tothe inlet orifice.
 3. The pump structure of claim 1 in which said platehas vanes on its lower surface for supporting the plate in spacedrelation to the lower end of the housing, said vanes directing liquidfrom the annular clearance to flow under the plate to the inlet orifice.4. The pump structure of claim 3 in which the vanes are curved radiallyof the plate.